1. Field of the Invention
The present invention relates to a guide wire used for introducing a catheter into a body cavity such as a blood vessel.
2. Description of the Related Art
For example, in case when a catheter is introduced into a blood vessel in the vicinity of the heart, such as the coronary artery, a guide wire is inserted through the catheter and the distal end of the guide wire goes ahead of the catheter while a desired path is properly selected whenever the guide wire meets a diverging point of blood vessels as branching off like a labyrinth.
Such a guide wire was disclosed by the gazette of U.S. Pat. No. 4,538,622. The guide wire is equipped with a wire body, which is a cylindrically shaped element, a first metal coil, a second coil, and a rounded structure. The first coil is fixed to the distal end of the wire body. The second coil is fixed to the distal end of the first coil. The rounded structure is fixed to the second coil. The jointed part of the first and the second coils is fixed to the wire body, which is inserted through the coils, by means of a soldering or brazing material. The brazing material and the rounded structure is bridged by a safety ribbon (refer to FIG. 2 and others of the above gazette).
It is found that a doctor who uses such a guide wire often bends the distal end of the guide wire in a certain desired shape in order to match the shape of the distal end of the catheter with the shapes of blood vessels or in order to guide it more smoothly around the branching points of blood vessels. Bending the distal end of the guide wire in a desired shape is called shape giving, or reshaping.
In case of the guide wire of the aforementioned U.S. Pat. No. 4,538,622, the safety ribbon is a separate component independent from the first coil and the second coil. Therefore, it presents a shortcoming that the fixed end of the safety ribbon may come loose when the safety ribbon is under a tensile strength during the reshaping process. When there is a concern for the safety ribbon to come off, the distal end of the guide wire cannot be formed into a desired shape and a sufficient reshaping effect may not be achieved.
When the wire body is made of Ni—Ti alloy for the benefit of super elasticity, the reshaping process is particularly difficult. Thus, it is necessary to provide a safety ribbon made of a material that can be reshaped easily such as stainless steel separate from the wire body.
Moreover, if the wire body is made of a Ni—Ti alloy, the wettability of soldering is poor, thus resulting in poor joint strength. Therefore, although the safety ribbon is provided, the fixation of the wire body and the coil or others can come loose, so that the safety ribbon, which is provided independently, can also come loose due to the force applied during the reshaping process.
In order to increase the joint strength of soldering, it is necessary to use a special procedure of covering the area with a preliminary tin while shutting out the contact with air after removing the oxide layer on the metal surface of the Ni—Ti alloy. This requires additional time and labors in the manufacturing process.
Those are the reasons why the selection ranges of the materials for the wire body and the safety ribbon are substantially narrowed. This makes it difficult to achieve the objective of reshaping, especially, in maintaining an appropriate flexibility in the distal end of the guide wire.